Apparatus for improving radio frequency signal transmission through low-emissivity coated glass

ABSTRACT

A method and apparatus for modifying low emissivity (low-E) coated glass, so that windows using the processed glass allow uninterrupted use of RF devices within commercial or residential buildings. Glass processed in the manner described herein will not significantly diminish the energy conserving properties of the low-E coated glass. This method and apparatus disrupts the conductivity of the coating in small regions. In an embodiment, the method and apparatus ablates the low-E coating along narrow contiguous paths, such that electrical conductivity can no longer occur across the paths. The paths may take the form of intersecting curves and/or lines, so that the remaining coating consists of electrically isolated areas. The method and apparatus are applicable both to treating glass panels at the factory as well as treating windows in-situ after installation.

This patent application is a continuation of U.S. patent applicationSer. No. 14/044,031, which was filed on Oct. 2, 2013 and is incorporatedherein by reference in its entirety.

BACKGROUND

In the interests of conserving energy, windows with a low emissivity(low-E) coating have grown in popularity over the years. Such windowsare now common in new commercial construction. These windows offer thebenefits of conserving energy and money by reducing the need for airconditioning and/or heating. However, such windows have a severe impacton radio frequency (RF) signals. The coatings that are applied to windowglass to transform it to a low-E window are comprised mainly of metals.Although the coatings are thin and transparent, their metallic contentis effective at conducting electricity. This makes the coatingsefficient reflectors of broad bands of radio frequency signals. Signalstransmitted through the windows can be attenuated at levels of 30decibels (dB) or more. Furthermore, commercial construction tends to useother materials that further block RF signals. Materials such asconcrete, brick, mortar, steel, aluminum, roofing tar, gypsum wallboard, and some types of wood all offer varying degrees of RFabsorption. The result is that many newer commercial buildings severelyimpede RF signals from getting into or out of the buildings.

Nonetheless, RF devices have become an important part of modern life,especially with the emergence of smartphones, which have a variety of RFdevices built-in. Such devices may include cellular transceivers,wireless local area network (“wi-fi”) transceivers, Global PositioningSystem (GPS) receivers, Bluetooth transceivers and, in some cases, otherRF receivers (e.g., FM/AM radio, UHF, etc.). As the popularity of suchdevices has grown, the importance of being able to use RF-based featureswithin the confines of modern commercial buildings has grown.

Currently there are several commercially available techniques tofacilitate the use of smartphones or similar devices within affectedbuildings. All of these techniques pose challenges, both for theinstaller as well as the user, depending on the technique. They includethe following:

First, an external antenna can be connected to most cell phones in orderto improve antenna gain. However, there still must be sufficient signalwithin the building and the cell phone must remain connected via acable. This solution can be inconvenient and has performance limitationsin some circumstances.

Second, a femtocell can be used. A femtocell is a device that resemblesa wireless router and can be purchased from mobile service providers.This device connects to an existing broadband internet connection in ahome or office, and radiates cell phone signals to a maximum range ofabout 40 feet. The maximum coverage per device is approximately 5000square feet. Depending on the mobile provider, these devices can supportbetween four and 16 simultaneous calls and require data bandwidths ofgreater than 1.5 Mb/s. Typically, prepaid phones are not supported withthis solution. Also, these devices must be located near a window toprovide a GPS signal. However, while a femtocell will support cellularsignals, low-E coated windows still block GPS signals. This latterproblem can be addressed by an external GPS antenna connected to thefemtocell. Although connections initiated via the femtocellautomatically connect to cell towers when the phone moves outdoorsduring a call, it does not work the other way—calls are dropped if theconnection is established outdoors via a cell tower and the phone isthen moved indoors where a femtocell is located. Another disadvantage ofusing femtocells in office buildings is that they are not universal forall mobile providers. A different femtocell must be purchased and set upfor each provider.

The third solution is the deployment of a cellular repeater or boosterthat consists of an external antenna, a bi-directional amplifier, andinternal antennas for re-transmission. These can be installed byindividual carriers, whose equipment will only work for that carrier, orby independent installers who can provide multi-carrier and multi-bandequipment. Second generation (2G) and third generation (3G) technologiesall operate in the 850 MHz (cellular) and 1900 MHz (PCS) bands. Allmajor carriers (e.g., Verizon, AT&T, Sprint and T-Mobile) operate inthis dual-band region. Fourth generation (4G) systems operate at 700MHz, 1700/2100 MHz and require different antennas than the 2G/3G dualbands. Most currently deployed repeaters were designed for 3G technologyand do not operate at 4G frequencies. 5-band amplifiers, which operateover both 3G and 4G bands, have recently become available, but arelikely not compatible with currently deployed antennas and will probablybe incompatible with the next generation of cellular hardware. Cellularrepeaters also do not boost Wi-Fi, WiMax and other signals in the 5 GHzband. In general, the use of repeaters will constantly require upgradesas technology advances.

There are additional limitations to the use of repeaters. Mostapplications require a custom installation. There must be room forantennas to be placed on the roof and cables must be run from them tointerior locations. There is also a tradeoff between using antennaswhich provide a high gain but are unidirectional, and thus only boostsignals from a single cell tower, and omni-directional antennas thatprovide less gain. The strongest amplifiers have enough gain to provideindoor coverage of up to about 100,000 square feet. This number istypically much lower, though, due to interior building materials thatprovide obstacles to the signal and unusual building geometries. Inaddition, concrete and steel floors significantly attenuate the signals,resulting in the need for separate amplifiers on every floor. Moreover,the cost of outfitting a commercial building can exceed $10K per floor.

BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES

FIG. 1 is a diagram showing the results of ablation of a low-E coating,according to an embodiment.

FIG. 2 illustrates a series of ablated spots, according to anembodiment.

FIGS. 3 a-3 d illustrate possible patterns of ablation, according to anembodiment.

FIG. 4 illustrates a process and apparatus for ablation, according to anembodiment.

FIG. 5 illustrates an apparatus for ablation, according to anembodiment.

FIG. 6 illustrates the apparatus of FIG. 5 from a side view, accordingto an embodiment.

In the drawings, the leftmost digit(s) of a reference number identifiesthe drawing in which the reference number first appears.

DETAILED DESCRIPTION

An embodiment is now described with reference to the figures, where likereference numbers indicate identical or functionally similar elements.While specific configurations and arrangements are discussed, it shouldbe understood that this is done for illustrative purposes only. A personskilled in the relevant art will recognize that other configurations andarrangements can be used without departing from the spirit and scope ofthe description. It will be apparent to a person skilled in the relevantart that this can also be employed in a variety of other systems andapplications other than what is described herein.

The following describes a method and apparatus for modifying low-Ecoated glass, so that windows using the processed glass allowuninterrupted use of RF devices within commercial or residentialbuildings. The method and apparatus are applicable to treating glasspanels at the factory before installation, as well as treating windowsin-situ after installation. At the same time, glass processed in themanner described herein will not significantly diminish the energyconserving properties of the low-E coating.

This method and apparatus for improving RF transmission through low-Ecoated glass involves a permanent change to the low-E coating on thewindow. The coating is normally conductive over the entire area of theglass; this method and apparatus disrupts the conductivity of thecoating in small regions. In an embodiment, the method involves ablatingthe low-E coating along narrow contiguous paths, such that electricalconductivity can no longer occur across the paths. The paths may takethe form of intersecting curves and/or lines, so that the remainingcoating consists of electrically isolated areas.

In an embodiment, this process is performed using a pulsed laser toremove (i.e., ablate) the low-E coating. In this method, the pulsedlaser is focused onto the surface of the sheet of glass where thecoating is located. With each pulse of the laser, a small (e.g. 20-25micron diameter) circular spot is ablated from the glass, permanentlyremoving it. In alternative embodiments, the ablated spot may beanywhere from 10-200 microns in diameter. By pulsing the laser manytimes per second (e.g. 100 kHz in an embodiment), while simultaneouslymoving the laser over the low-E coating, a path of overlapping ablatedspots results, creating the appearance of a thin line (in much the samemanner that a laser printer creates the appearance of a line on paper).The line can be straight or curved, and normally for a large windowthere will be many such lines that are ablated, with the spacing of thelines or curves depending on the desired characteristics of the RFreception through the glass.

Due to the nature of low-E coatings, their energy conserving propertiesare largely unaltered by such ablation if the total area of ablation iskept small. For example, if a window has a series of lines ablated intothe coating, but the total area of the lines is kept small (e.g. <2% ofthe total glass area), then the impact to the energy conservingproperties will be similarly small, and therefore acceptable for mostapplications.

The impact on RF signal transmission through the window, however, is nota simple function of ablated area. For example, a low-E coated windowthat has had only 1% of its area ablated with a regular grid pattern canexperience a much greater throughput benefit than might be suggested byonly having 1% of the area ablated. RF testing has confirmed that thisis the case, showing that for some ablation patterns, a 1% area ablationof simple grid lines can change the insertion loss of such a window fromover 35 dB (less that 1/10th of 1% throughput) prior to ablation to lessthan 10 dB (nearly 10% throughput) after ablation, which is asignificant improvement. Alternatively, a low-E coated window that hashad 1% of its area ablated will only have its infrared-reflectingproperties reduced by 1%. Therefore a very small change to the infraredproperties of the low-E coating can result in a very large benefit inthe RF transmission properties.

FIG. 1 illustrates a side view of a coated glass pane that has undergonethe process described herein, according to an embodiment. A glass pane110 is shown with a low-E coating 120. An ablated region 130 is shown.Here, the low-E coating 120 has been removed by laser ablation.

In an embodiment, a pulsed laser may be used, where each pulse deliversenough energy to ablate a spot of the low-E coating 120. The laser ismoved in a plane that is approximately parallel to the glass as itoperates. The laser moves across the glass in a linear or curvilinearmanner. The result is shown in FIG. 2, according to an embodiment. Asequence of ablated spots 210 is formed. This creates a path 200 inwhich the low-E coating 120 has been removed. As will be described ingreater detail below, a series or pattern of intersecting ablated pathsmay be created in the coating, while leaving behind the coating inuntouched areas. In an embodiment, only a very small percentage of thearea of the low-E coating is removed from the glass, and most of thecoated glass remains untouched. These paths are produced in such a wayas to create areas of the low-E coating that are electrically isolated.This permits the glass to retain most of its energy conservingproperties, while the ablated paths allow passage of RF signals throughthe glass. In various embodiments, a spot 210 may be 20-25 μm indiameter, so that each path will be approximately this width. Inalternative embodiments, different sized spots (e.g., 10-200 microns indiameter) and paths may be used. Moreover, in the illustratedembodiment, the spots overlap. In an embodiment, the amount of overlapmay be approximately 50% by area; the extent of overlap may vary inalternative embodiments. In some embodiments, the overlap may range from25% to over 90% for example.

The pattern of ablated intersecting paths may be varied. Variousgrid-like patterns that may be used are illustrated in the embodimentsof FIGS. 3A-3D. In FIG. 3A, a series of paths 303 are created as linesegments in essentially vertical and horizontal orientations. Thisleaves behind areas of low-E coating (such as region 306) that areelectrically isolated from each other. A different pattern isillustrated in FIG. 3B. Here, the horizontal path segments aredisjointed. As in the previous case, regions of low-E coating are leftbehind, such as region 326.

In alternative embodiments, the ablated intersecting paths are notnecessarily limited to horizontal and vertical line segments. As shownin the embodiment of FIG. 3C, the ablated paths 333 may create ahoneycomb pattern, creating regions of low-E coating 336. Anotherembodiment is illustrated in FIG. 3D, where the ablated paths 343 takethe form of circles that touch each other. As in the previous examples,coated regions remain, such as regions 346 both inside and outside thecircles. Alternative patterns, apart from those illustrated here, mayalso be employed. No particular pattern is necessarily superior toanother, unless enhanced transmission of RF signals of a particularpolarization is desired.

In embodiments, the ablated area of a window may be 2% or less of thetotal area. In other embodiments, a different percentage may be used.Note that while ablation of a higher percentage of the area may improvethe transmission of RF signals through the window, ablation of more ofthe low-E coating diminishes the energy conserving properties of thewindow.

In embodiments, the grid spacing can be range from 2-10 mm. In general,smaller isolated areas of low-E coating facilitate improved RFtransmission at shorter wavelengths, whereas larger overall size of theentire ablated pattern tends to facilitate longer wavelengths. Patternsthat need to allow for transmission of multiple RF frequencies, whileproviding maximum transmission across all those frequencies, may have anoverall ablation area dictated by the longer wavelengths whilesimultaneously having the grid/line spacing dictated by the shorterwavelengths.

The overall area of the pattern may vary in different embodiments.Larger patterns, by overall area, generally allow improved RFtransmission. In some situations, however, the permissible area for apattern may be limited. In such a case, transmission of RF signals maystill be improved if the pattern area has a length and width in excessof approximately two times the wavelength of the RF signal.

An apparatus for the ablation of low-E coating is illustrated in FIG. 4,according to an embodiment. Glass pane 110 is shown, having low-Ecoating 120. A pulsed laser 410 creates the necessary light andtransmits it through a fiber optic line 420. In the illustratedembodiment, laser pulses exit a fiber tip. The beam expands and passesthrough a set of lenses (lens array 440) in order to focus the light. Inthe illustrated embodiment, the lens array 440 is contained in a lenshousing 430. Incident light 450 strikes the coating 120 at a point ofincidence 460. In an embodiment, it may be desirable for the light tostrike the coating 120 at a non-normal angle. This would avoidreflection of the light back into the lens array 440.

Note that in some situations, the coated glass pane 110 may be part of adouble pane window. Such a configuration is common in modernconstruction. The second pane is shown in FIG. 4 as glass pane 405. Thelow-E coating 120 typically resides on the inside surface of one of thepanes. In the illustrated embodiment, the light passes through glasspane 405 before striking the coating 120 on the other pane. In analternative embodiment (not shown), the coating may be present on thepane closest to the laser, in which case ablation would be performed onthe inside surface of the closer pane.

The wavelength of the laser used in various embodiments may differ. Insome embodiments, the wavelength may be greater than 1400 nm. Suchwavelengths have the advantage of providing improved eye safety to theoperator and nearby persons compared to shorter wavelengths. In analternative embodiment, the wavelength may be 1064 nm, which is acommonly used wavelength for marking lasers. Moreover, as noted above,in an embodiment the laser 410 is a pulsed laser. In an embodiment, thepulse width is less than 10 nanoseconds (ns), although pulse widths asgreat as 100 ns or longer may be used. Further, in an embodiment eachpulse delivers at least 3 microjoules (μJ) of energy. In alternativeembodiments, values of these parameters may differ as will be understoodby a person of ordinary skill in the art.

Ablation may be performed on a window during the manufacturing processor during or after the installation process. In an embodiment, ablationmay be performed on a window that is already in place in an existingwall. An apparatus 500 for performing this process in such a context isillustrated in FIG. 5, according to an embodiment. Here, a double paneglass window is shown after having been installed in a wall 505. In thisexample, there are two panes of glass in the window, 110 and 405. In theillustrated embodiment, the apparatus includes four mounts 507 a-507 dfor attachment to the window. In an embodiment, mounts 507 a-507 d maybe suction cups. Other embodiments may use other means for attachment tothe window or to the surrounding wall 505, as would be understood by aperson of ordinary skill in the art.

In the illustrated embodiment, the pulsed laser 410 is attached to arail 540 in a manner that allows the laser to slide or otherwise movealong the length of this rail. In particular, the pulsed laser 410 andlens array 440 may be attached to a mount 570 that is attached to a belt560 incorporated into this rail length wise. The belt 560 may be mountedon two pulleys, 550 a and 550 b at either end of rail 540. The belt 560is therefore movable; movement of the belt serves to move the pulsedlaser 410 and lens array 440 mounted thereon. One of the pulleys may bedriven by a motor 545. In the illustrated embodiment, motor 545 turnspulley 550 a, thereby driving the belt 560. This in turn moves thepulsed laser 410 and its lens array 440 along the length of rail 540 (upand down in the illustrated embodiment). The motor 545 maybe capable ofturning in either direction, so that the belt 560 may move in eitherdirection, as shown. In this way, the laser 410 may be moved in eitherdirection along rail 540. In an alternative embodiment, the motor 545may be mounted at the opposite end of rail 540 to drive pulley 550 b. Inyet another embodiment, two motors may be used, one at each of pulleys550 a and 550 b, and operating in synchronicity.

In the embodiment of FIG. 5, the rail 540 may in turn be mounted on twoother rails, 510 a and 510 b. These latter two rails are essentiallyparallel to each other. One end of rail 540 may be mounted on rail 510 aby means of a mount 530 a; similarly, the opposite end of rail 540 maybe mounted on rail 510 b by means of a mount 530 b. The ends of rail 540may be mounted on rails 510 a and 510 b such that rail 540 may slide orotherwise move along the lengths of rails 510 a and 510 b (side to sidein the illustrated embodiment).

Here, rail 510 a includes a belt 520 a that is mounted on two pulleys515 a and 515 b at either end of rail 510 a. The mount 530 a is attachedto this belt. Similarly, rail 510 b includes a belt 520 b that ismounted on two pulleys 515 c and 515 d at either end of rail 510 b. Themount 530 b is attached to this belt. Pulley 515 c is driven by a motor512 b. This serves to move belt 520 b. Likewise, pulley 515 a is drivenby a motor 512 a, which serves to move belt 520 a. By synchronizing theactions of motors 512 a and 512 b, belts 520 a and 520 b may besimultaneously moved in the same direction at the same speed. Given thatrail 540 is mounted on the belts 520 a and 520 b, this serves to moverail 540. The motors 512 a and 512 b can turn in either direction; thisallows respective belts 520 a and 520 b to move in either direction, asshown. As a result, rail 540 (and pulsed laser 410 and lens array 440,which are attached to this rail) can be moved from side to side in theillustrated embodiment.

In alternative embodiments, motors 512 a and 512 b may instead beattached to pulleys 515 b and 515 d. Moreover, in other embodiments, anyor all of the pulleys 515 a-515 d may be driven by motors that aresynchronized to one another.

The combined motions of belts 520 a, 520 b, and 560 allow the pulsedlaser 410 and lens array 440 to move about in a two-dimensional planethat is essentially parallel to the window. By controlling the speed anddirection of motors 512 a, 512 b, and 545, the laser 410 and lens array440 can be made to move over the window in any desired path. Byenergizing the pulsed laser 410 while in motion, a path can be ablatedin the low-E coating of this window.

In an embodiment, the motors 512 a, 512 b, and 545 may be controlled bya programmable computer (not shown). By programming this computerappropriately, the computer can be made to create and deliver controlsignals to these motors to control the motion of the pulsed laser 410and lens array 440, and thereby control the path and pattern ofablation. For example, the apparatus 500 may be used to create any ofthe patterns illustrated in FIGS. 3A-3D. Alternatively, the motors maybe controlled by hardwired logic instead of a computer executingsoftware. Alternatively, the motors may be controlled by hand.

As noted above, other patterns may be created, different from or inaddition to these. In an embodiment, the pulsed laser 410 and lens array440 can be made to move at an overall speed of 1 m/s; other speeds arepossible.

In an embodiment, the motors illustrated in FIG. 5 are electrical. Theymay be stepper motors or non-stepper (e.g., servo) motors. Inalternative embodiments, belts such as those shown may not be used;instead, a linear actuator may be used to move the pulsed laser 410along rail 540. Likewise, linear actuators may be used to move the rail540 from side to side along rails 510 a and 510 b. Such actuators may bepneumatic, hydraulic, or electromagnetic, for example.

Also, while FIG. 5 shows the pulsed laser 410 moving along vertical rail540, which in turn is moved along the horizontal rails 510 a and 510 b,other orientations are possible. For example, rails 510 a and 510 b maybe attached to the window vertically, and rail 540 may be orientedhorizontally. Also, rail 540 is shown in this figure to be approximatelyperpendicular to rails 510 a and 510 b. In other embodiments, this isnot necessarily the case; rail 540 may reside at some other anglerelative to rails 510 a and 510 b. In addition, FIG. 5 shows apparatus500 positioned vertically on a mounted window. Alternatively, theapparatus 500 may be positioned horizontally to operate on an unmountedwindow that is lying flat, prior to the window's installation, or tooperate on a coated sheet of glass prior to the glass being incorporatedinto a double pane window.

FIG. 6 illustrates a side view of the apparatus of FIG. 5. A low-Ecoating 120 is shown on glass pane 110, which is incorporated along withglass pane 405 in a double pane window. Pulsed laser 410 is shownattached to mount 570. Lens array 440 is also attached to mount 570, viaa bracket 620. Mount 570 is attached to belt 560 which is in turnmounted on pulley 550 a and pulley 550 b (which is not visible here). Asstated above, the motion of belt 560 allows for the vertical movement ofpulsed laser 410 and lens array 440 in the illustrated embodiment.

One end of rail 540 is mounted on belt 520 a, which is in turn mountedon a pulley 515 a and a pulley 515 b (not shown). These pulleys, alongwith belt 520 a, are incorporated in rail 510 a. The near end of thisrail is attached to the window by a mount 507 a and support block 610. Asimilar mounting configuration may be in place at the far end of rail510 a. Pulley 515 a is turned by motor 545 a, thereby moving belt 520 aand rail 540. A similar configuration is present at the opposite end ofrail 540. As stated above, this allows for horizontal movement of pulsedlaser 410 and lens array 440.

In embodiments, the laser 410 may be supported by a spring mechanism(not shown). For example, a constant force spring may be used along they-axis to support the laser 410 and reduce mechanical stress in theillustrated system.

Note that all the rails are approximately parallel to the glass. Thisallows the laser to operate in a plane that is approximately parallel tothe glass, maintaining the focused laser spot on the low-E coatingacross the entire ablation pattern area. In embodiments, the rails arewithin 500 microradians of parallel.

While the embodiments described above address ablation using amechanically scanned laser, in alternative embodiments other methods maybe used to remove or create the absence of a low-E coating to achievethe results exemplified in FIGS. 3A-3D and FIG. 1. An optically scannedlaser may be used to produce the specified electrically isolated areasin the low-E coating. In such an embodiment, the laser beam may bedirected at the necessary locations on the low-E coating by a system ofone or more mirrors. Alternatively, mechanical abrasion methods may beused to remove the coating; a photolithographic method and acid etchingmay also be used. Alternatively, an electric discharge machine may alsobe used. In alternative embodiments, all of these techniques (includinglaser ablation) may be employed alone or in any combination to removeportions of a low-E coating from a sheet of glass.

Another embodiment for achieving the results exemplified in FIGS. 3A-3Dand FIG. 1 could involve the use of ink jet printing techniques fordepositing the low-E coating onto the glass surface in such a way as tointentionally leave areas without any coating to form the describedpatterns. Alternatively, a shadow mask could be used to intentionallynot coat portions of the glass and form the described patterns.

An alternative process for achieving some transmission of RF signalsthrough a low-E coated window is to purposely fabricate the glass withlarge areas free of low-E coating. An example that would provide somebenefit is to leave a border around the entire edge of the window thatis not coated.

As noted above, the processing of a sheet of glass according to some ofthese methods may be performed on an installed window. Any of thetechniques may be performed at a factory prior to installation. In thislatter case, the processing may be completed on a single glass sheet ata time, or an assembly line style operation may be used. Here, multiplestations may be involved. Each station would perform ablation (orremoval by other means) of the low-E coating along one or more paths,then would send the glass sheet to another station, where removal of thecoating along one or more other paths may be performed, and so on. Aswould be understood by a person of ordinary skill in the art, such anarrangement would improve throughput at a processing or manufacturingfacility.

Methods and systems are disclosed herein with the aid of functionalbuilding blocks illustrating the functions, features, and relationshipsthereof. At least some of the boundaries of these functional buildingblocks have been arbitrarily defined herein for the convenience of thedescription. Alternate boundaries may be defined so long as thespecified functions and relationships thereof are appropriatelyperformed.

While various embodiments are disclosed herein, it should be understoodthat they have been presented by way of example only, and notlimitation. It will be apparent to persons skilled in the relevant artthat various changes in form and detail may be made therein withoutdeparting from the spirit and scope of the methods and systems disclosedherein. Thus, the breadth and scope of the claims should not be limitedby any of the exemplary embodiments disclosed herein.

What is claimed is:
 1. An apparatus for modifying a low emissivity(low-E) coating on a sheet of glass, the apparatus comprising: a laser,a lens array configured to focus said laser on locations on the low-Ecoating; and two or more motors of which at least one motor isconfigured to control the position and movement of the laser in a firstdirection essentially parallel to the glass, and at least one othermotor is configured to control the position and movement of the laser ina second direction that is orthogonal to the first direction andessentially parallel to the glass, wherein said two or more motors areconfigured to move said laser in such a manner as to ablate intersectinglines or curves in the low-E coating, creating electrically isolatedareas of remaining low-E coating, wherein said laser is configured toablate the low-E coating at the locations along which said laser isdirected as said laser is moved.
 2. The apparatus of claim 1, furthercomprising: a programmable processor configured to create and sendcontrol signals to the two or more motors wherein said control signalscontrol the speed and direction of said motors.
 3. The apparatus ofclaim 1, wherein said lens array is oriented to direct said laser suchthat the angle of incidence of said laser is not normal with respect tothe sheet of glass.
 4. The apparatus of claim 1, wherein said laser ispulsed.
 5. The apparatus of claim 4, wherein the width of each pulse isless than or equal to 100 nanoseconds (ns) and wherein said laser isconfigured such that each pulse delivers 3 microjoules or more ofenergy.
 6. The apparatus of claim 4, wherein said laser is configuredand positioned to ablate a spot of the low-E coating measuring 10 to 200microns in diameter.
 7. The apparatus of claim 4, wherein successivespots, which are ablated by said laser as it moves, overlap by 25% toover 90% by area.
 8. The apparatus of claim 1, wherein said laser isconfigured to operate at a wavelength greater than or equal to 1400 nm.9. The apparatus of claim 1, wherein said laser is configured to operateat a wavelength of approximately 1064 nm.
 10. The apparatus of claim 1,wherein said two or more motors are configured to move said laser at avelocity of approximately 1 meter per second.
 11. The apparatus of claim1, further comprising a first rail, wherein said laser is movablymounted on said first rail, such that one or more of said two or moremotors are configured to move said laser along said first rail in thefirst direction.
 12. The apparatus of claim 11, further comprising asecond and third rail, such that a first end of the first rail ismovably mounted to the second rail, and a second end of the first railis movably mounted to the third rail, wherein the second and third railsare essentially parallel to each other and wherein one or moreadditional motors of said two or more motors are configured to move thefirst end of the first rail along said second rail in the seconddirection and simultaneously move the second end of the first rail alongsaid third rail in the second direction.
 13. The apparatus of claim 12,wherein said first rail comprises a first belt mounted on a first pulleyat the first end of the first rail, and on a second pulley mounted atthe second end of the first rail, wherein said one or more motors areconfigured to drive the first belt around said first and second pulleys,and wherein said laser is mounted on said first belt so that driving thefirst belt causes the laser to move along the first rail.
 14. Theapparatus of claim 13, wherein the second rail comprises a second beltmounted on a third pulley at a first end of said second rail, and on afourth pulley at a second end of said second rail, wherein the thirdrail comprises a third belt mounted on a fifth pulley at a first end ofsaid third rail and on a sixth pulley at a second end of said thirdrail, wherein said one or more additional motors are configured to drivesaid second and third belts simultaneously in the second direction,wherein the first end of the first rail is mounted on the second beltand the second end of the first rail is mounted on the third belt, andwherein driving of the second and third belts in the second directioncauses said first rail and said laser mounted thereto to move in thesecond direction.